"Freedom of movement is considered a basic human right by the majority of countries of the world. As defined in practice, it encompasses the right to move internally within a country, the right to move abroad, and the right to return from abroad. It does not include the right of an individual from one sovereign nation to move to another. In this paper, I examine whether there is an economic rationale for restricting the rights of individuals to move across borders. The typical individual who migrates from a poor developing country to the United States sees an increase in income by a factor of four, largely as a result of the immense international differences in labor productivity that exist in the world today. As an illustrative example, I estimate that migration from Mexico to the United States raises global income by an amount equivalent to roughly one percent of US GDP"--National Bureau of Economic Research web site.